1. Technical Field
The present invention relates to temperature sensor devices and more particularly to a circuit device that is compatible with integrated circuit technology and converts a change in temperature in its immediate environment to a proportional electrical current.
2. Background Art
Many devices are available for sensing temperature. Examples of such devices includes thermocouples, thermistors, silicon resistors, special wire wound resistors, bi-metallic devices, thermometers, etc. Especially desired are devices that depend on basic physical constants as opposed to devices that are subject to variation of properties due to process variations. Most available discrete devices for temperature sensing are not compatible with integrated circuit technology. That is they cannot be placed on a silicon chip with other circuitry utilizing a standard process. Some techniques have been developed which utilize an integrated resistor or diode for sensing. This technique results only in approximately a linear variation in the device parameter with temperature. In some cases it may be desirable to have a nonlinear or rapidly changing response to temperature so that a switching action may be directly obtained. A switching type device will change several orders of magnitude at the switching temperature and therefore is of a nonlinear nature.